Centrifugal refrigerant compressors are known, and include one or more impellers driven by a motor. During operation of a centrifugal compressor, refrigerant is expelled outward from the impeller. One known compressor type includes a vaneless diffuser configured to regulate the flow of fluid expelled by the impeller. Another known compressor type includes a vaned diffuser. Vaned diffusers are known to include mechanical and/or hydraulic actuators capable of either turning the diffuser vanes or moving a sidewall relative to the diffuser.